Optimization of Drilling Parameters in Drilling of Geothermal Wells - A Case Study of Well MW-17 in Menengai Field

Abstract

Several factors come into play when the drilling bit is crushing rocks at the bottom of the hole. To effectively drill geothermal wells, these factors must be carefully considered and combined in an optimum manner. The characteristic of geothermal formations is such that it is composed of different layers of rocks alternating from the surface to the final depth. Some rocks are highly altered while others are highly fractured and unconsolidated. A careful approach has to be devised while drilling through the different sections to avoid problems which lead to delays in drilling. At the same time drilling parameters have to be applied according to the rock types in such a way that the well is drilled in the shortest time possible and in the most cost effective manner. The following factors have been identified and mathematically modeled by multiple linear regression and each factor studied how it affects the overall drilling rate: Formation strength, Formation depth, Formation compaction, Pressure differential across the hole bottom, Bit diameter and bit weight, Rotary speed, and Bit hydraulics. Thereafter drilling was optimized by optimizing bit weight, the rotation speed and the bit hydraulics. Data captured while drilling of well MW-17 in Menengai geothermal field was used in making the drilling model. A combination of Excel and Matlab was used in the data analysis.